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2 Sheets-Sheet 2.

(No Model.)

C. A RANDALL. TELEPHONIG TRANSMITTER.

V |NvE'NToR ZwrZesdMuavZ ATTORNEY N. PETERS. Ppm-Lummpw. wnshingm D. c;

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, cHAELEs AEANDALL, oE NEW vonk, N. Y.

TELEPHONIC TRANSVITTER.

SPECIFICATION forming` part of Letters Patent No. 295,805, dated March25, 1884.

Application filed May 3, 1883. (No model.)

.To @ZZ whom .it `may concern.- j

I Be' it known that I, GHAnLEs ARANDALL, a citizen of the United States,residing at New "York, in the county and State of N ew York,

have invented new and useful Improvements in Telephonic Transmitters, ofwhich thefollowing is a specification.

This inventionrelates to improvements in that class of telephonietransmitters known as lever-transmitters,77 in which the vibrations ofthe diaphragm are transmitted to the current-varying contacts by meansofan am- Vpliiying-lever.` In transmitters of this class as heretoforeconstructed and provided with metallic diaphragms which expand and con-`tract withvariations of temperature, or diaphragms formed of materialwhich is affected by the hygrometric condition of the atmosphere, therehas been experienced great diiiiculty in maintaining a proper adjustmentof the contact point or points upon which the lever acts, from the factthat a very slight expansion or contraction of the diaphragm with whichthe short arm of the lever is connected bon or slate disk, whereby thediaphragm will not be expanded `or contracted by variations oftemperature, and hence not throw the lever out ofproper relation to thecircuit-varying contacts upon which it is to act.

My invention also consists in certain improved details of constructionfor promoting efficient action of transmitters of this class, as willbehereinafter particularly described, and pointed out in the appendedclaims. v

In the accompanying drawings, Figure l is a side elevation of atelephonie transmitter constructed according to my invention. Fig. 2 isa rear view of the same. Fig. 3 is a side view, partly in elevation andpartly in section onthe `line m r of Fig. 2. Fig. 4L is a sectionalview,illustrating amodiiication of the devices for regulating thetension of the contact-points uponwhich the lever acts. Fig. 5 is a sideingB. The inner end of this block is recessed to receive a metallicdisk, I, having a central opening, as at t', the diaphragm D beingsecured at the rear of I and at its margin or edge by a suitableclamping-ring, d, through which screws take into the body of the blockA. l

.E indicates the ordinary mouth-piece, which is secured to the frontwall ofthe casing around a suitable opening, from which a funnel-shapedpassage, if, extends through the block A, and terminates inwardly attheopening in the disk I. The diaphragmsupporting block A being ofinsulating material `and of not very great vibratory quality, the diskI, of vibratory material, is recessed therein, in order to convey asstrongly as possible to the diaphragm such vibrations'as strike andexpand themselves upon the sides of the opening in A, instead of beingconveyed. directly through the opening in the disk to the diaphragm. Bythe described constructionoi the diaphragmsupporting block A and disk I,a chamber is formed in front of the diaphragm and between `it and themouthpiece, by which a considerable body of air is maintained in frontof the diaphragm, and serves as a cushion to re-enforce the action uponthe diaphragm of the sound-vibrations which are projected against itthrough the opening in the disk. The diaphragm D is made of carbon orslate, or any material having similar characteristics,for the purposehereinbefore stated.

F is the amplifying-lever, made preferably of wood or other lightnon-conducting material. "and fulcrumed on a cross-bar, di, secured tothe ring d. The upper end ofthe short arm f of this lever is connectedloosely toa stud, d, which is secured to and projects rearwardly fromthe center of the diaphragm, a pin, d2, being securedto the stud andpassing loosely through an.` opening, o, in the lever. The lower longarm, f', of thelever is terminated by a small cylinder of car- IOO bon,f2, which is connected by an insulated wire, f3, with the metallicbearings of the lever. On opposite sides of the middle carbon cylinderare arranged elastic contact-terminals G and G of the battery-circuit.Each of these terminals consists of acarbon contact-piece, g, carried atthe end of a sliding rod, g', which has its bearings in a standard, g2,secured to an adjustable base, g, and in a socketed adio justing-screw,g3, arranged in the top of another standard, g5, which is also securedto said adjustable base.

On the rod g', behind the standard g2, is a shoulder, S, against whichbears one end of a r 5 spiral spring, which surrounds the rod and hasits other end bearing against the tip of the socketed adjusting-screwgi.

From the rear side of the carbon contactpiece of the contact-terminal Gprojects a pin, 2o h, which passes loosely through an opening in thestandard g2, and serves to prevent said contact piece and its supportingrod from turning, as such turning might vary the adjustment of thecontact-piece, owing to lackv 2 5 of trueness of its surface or slightbending of its supporting-rod.

From the carbon contact-piece of the contact-terminal G projects an arm,y, the lower end of which has an opening, through which 3o looselypasses a headed screw, gl, which takes into the standard g2, whichsupports the said contact-piece and its rod. It will be observed that byadjusting the screw g7 I may regulate the extent of the movement of thecontact- 3 5 piece toward the carbon cylinder of the lever, and I amthus enabled to regulate the relation between this contact-piece and thecarbon cylinder of the lever when said lever moves toward the othercontact-piece. rlhe adjust- 4o able bases g4 g* slidein separatemetallic guidesgg, and are adjusted therein by means of adjusting-screwsgi, which project from each of the standards g5, and are provided withadjusting-nuts gw, arranged between stationary lugs gu. Thecontact-terminals, their supports, base-guides, and adjusting devicesare all supported by a non-conducting base-plate, 7c, which is carriedby an arm, L, projecting downward from and secured to the disk I. By

5o this arrangement I secure a common support for the diaphragm, thelever, and the contact deyices, which I find to be very advantageous, asthere is less liability of the parts getting out of adjustment than whenthey are separately supported. The contact-terminals G and G are tobeelectrically connected with the opposite poles of a battery, asindicated at N, by wires w w, which lead from the me- Y tallic guides,in which slide the metallic sup- 650 porting devices of the saidterminals. The center of the battery is connected to ,the ground. Thecontact carbon cylinder f2 of the amplifying-lever is connected by thewire f3, the metallic lever-bearings, metallic crossbar d3, and a wire,f4, with the line-wire direct or to the primary of an induction-coil, in

the usual manner, the opposite terminal of the primary in such casebeing connected to the ground or with the center of the battery, whichthen need not be connected with the ground. 1

This transmitter operates generally in the same manner as that shown anddescribed in my Letters Iatent No. 235,019, granted November 30, 1880,and may be used in connection with any of the ordinary magneto-receivingtelephones.

In the modification shown in Fig. 4 the rods which carry thebattery-terminals G and G abut at their rear ends against flexiblediaphragms, which form wallsl of mercury-cups m m, provided with adjustin g-screws m', which may be adjusted into the mercury and cause thesame to exert more or less tension on the said iiexible diaphragms. asdesired, for adj usting the ,resistance of the contacts to the action ofthe lever. In this modification the springs are omitted, the elasticdiaphragm serving in lieu thereof.

In themodiiication shown in Fig. 5the amplifying-lever F is fulcrumedatits upper end and intermediately connected with the stud whichprojects from the diaphragm D. 'Io the same pin which supports the leverare pivoted pendent metallic arms p p, which are insulated from saidpin, said arms being arranged on opposite sides of the lever F', andhaving their lower ends bent toward the contact-cylinder carried by saidlever, and provided with carbon contact-pieces g q', arranged to come inContact with the opposite ends of said cylinder, respectively. Thependent arms may be so shaped that their contact-pieces will comeagainst the contact-cylinder of the lever by gravity, and they may,besides, be connected by a spring, s, and adj Listing-screw s', providedwith a thumb-nut, s2, so that the pressure of the contact-pieces uponthe cylinder may be regulated. The upper ends ofthe arms p and p may beconnected by suitable wires, fw w', with the opposite poles of abattery, and the lever F may 'have its conta ct-cylinder connected withthe main line or an induction-coil by means of an insulated wire, fi. Inthis modification it will be seen that the currentvarying contacts aresupported independently of springs, and the vibrations of the lever aretaken off by contact-points necessarily moving in unison therewith andin the same circle. When theinstrument is not in use, the batterycurrentiiows through the two arms P l), their contact-pieces, and thecontact-cylinder of the lever; but when the diaphragm is set in motionthe pressure of the contact-cylinder upon the contact-pieces of the armsis so varied, increasing upon one While decreasing upon the other, thatthe battery-currents of opposite polarity are alternately directed overthe Wire f1, which connects the contact-cylinder of the lever with `themain line or induction-coil.

No claim is made herein to the construction shown in Fig. 5, although itembodies and car- IOO IIO

ries into effect the general principle hereinbefore laid down. It .willbe made the subject of a separate application.

Having thus described my invention, What I claim isl. In a levertransmitting-telephonc, the combination, With the amplifying-lever, of amotive diaphragm formed of a carbon or slate disk, substantially asdescribed.

2. In atelephonic transmitter, the combination, with the motivediaphragm, of a n1outhpiece and an air-ohamberinterposed between thediaphragm and mouthpiece,`said aircham ber being conical in form, itsgreater diameter being next to" and larger than the inner opening of themouth-piece, substantially as described. i

3. The combination, with the diaphragm, of `the amplifying -leverlloosely connected therewith, to have a slight play independently of thediaphragm, substantially as described.

4. The combination, with the amplifyinglever and its carbon or contactterminal and the battery terminals or contacts, of means, substantiallysuch as described, for adjusting the positions of said battery-terminalsrelatively to each other and the lever-terminal,

and separate means, substantially such as described, for adjusting theirnormal contact or pressure, substantially as set forth.

5. The combination, with a spring-seated battery-terminal, as shown anddescribed, of

support rising from and carrying or supporting the air-chamber block anddisk, and formingy a common support for the operative devices attachedto or controlled by the motive diaphragm, substantially as described.

In testimony whereof `I have hereunto set my hand in the presence of twosubscribing Witnesses.

C. A. RANDALL.

Vitnesses:

i J. W. HUGHES,

W. J. GAHooNn.

